Where To Find PageSpeed Insights
First of all, you need to go there where your websites are. This place is called SiteRubix - SiteManager.
Step 1. You find it by pressing the big light-blue button on the left called "SiteRubix" and then on the top option called "SiteManager".
Now you will get an overview of all your websites (or only one, if you got only one). I've got a couple, so my list is long.
For the purpose of this tutorial and the rules about what I can or cannot commercialize, I removed the domain names and username/passwords for my sites here.
Step 2. You will have to click on Details next to your sites' name.
Step 3. Go to PageSpeed Insights box
Now you will get a list of options and boxes. When you scroll down you will come to PageSpeed Insights. This box is available to any website (I tested it for both .siterubix.com sites as well as hosted domains), even when they haven't got any form of SiteSpeed enabled.
Step 4. Click on the 'Check' link next to each of the pages you would like to check.
It will be working on a result for a while (maybe up to a minute) and then display the result. In this case not the best of result I have to say.
You can check for multiple pages and it will stay the way it is scanned for until you click on 'refresh' one day in the near future to do another check. This could be a good idea to do after you have done alterations to your page/post to make the page faster.
Here's a picture of another one of my sites' PageSpeed Insights. Bit better results there (bootcamp site).
Next up: Using PageSpeed Insights